scholarly journals Vanadate inhibits degradation of short-lived, but not of long-lived, proteins in L-132 human cells

1989 ◽  
Vol 258 (1) ◽  
pp. 33-40 ◽  
Author(s):  
J L Vargas ◽  
F Aniento ◽  
J Cervera ◽  
E Knecht
Keyword(s):  
Protein Degradation ◽  
Cultured Cells ◽  
Human Cells ◽  
Lysosomal Degradation ◽  
Intracellular Degradation ◽  
Cell Extracts ◽  
Nutritional Conditions ◽  
Step Down ◽  
First Time

Vanadate, at concentrations higher than 0.04 mM, inhibits the intracellular degradation of short-lived proteins in exponentially growing L-132 human cells. The inhibition is not due to a decrease in viability or in the ATP contents of the cells. Since vanadate decreases proteolysis in cell extracts, the inhibition appears to affect the proteinases which degrade these proteins. Under optimal nutritional conditions, the degradation of long-lived proteins is accelerated by vanadate, thus providing additional evidence that in exponentially growing cultured cells degradation of short- and long-lived proteins occurs by different processes. Vanadate also efficiently inhibits the lysosomal degradation of endocytosed proteins and of long-lived proteins under step-down conditions. However, this effect seems to be unrelated to the observed inhibition of degradation of short-lived proteins, because chloroquine and leupeptin, which inhibit degradation of proteins by lysosomes, do not modify the degradation of these proteins. Our results provide for the first time a probe which, owing to its opposite effects on the degradation of short- and long-lived proteins, could be useful to clarify the mechanisms involved in protein degradation in cultured cells.

scholarly journals Characterization of peptidyl boronic acid inhibitors of mammalian 20 S and 26 S proteasomes and their inhibition of proteasomes in cultured cells

2000 ◽  
Vol 346 (2) ◽  
pp. 447-454 ◽  
Author(s):  
Robert C. GARDNER ◽  
Stephen J. ASSINDER ◽  
Gary CHRISTIE ◽  
Grant G. F. MASON ◽  
Roger MARKWELL ◽  
...  
Keyword(s):  
Protein Degradation ◽  
Boronic Acid ◽  
Cultured Cells ◽  
Gel Filtration ◽  
Boronic Acids ◽  
Cell Extracts ◽  
Catalytic Sites ◽  
Ic50 Values ◽  
In Cells

Proteasomes are large multisubunit proteinases which have several distinct catalytic sites. In this study a series of di- and tri-peptidyl boronic acids have been tested on the chymotrypsin-like activity of purified mammalian 20 S and 26 S proteasomes assayed with succinyl-Leu-Leu-Val-Tyr-amidomethylcoumarin (suc-Leu-Leu-Val-Tyr-AMC) as substrate. The inhibition of 20 S proteasomes is competitive but only slowly reversible. The Ki values for the best inhibitors were in the range 10-100 nM with suc-Leu-Leu-Val-Tyr-AMC as substrate, but the compounds tested were much less effective on other proteasome activities measured with other substrates. Free boronic acid inhibitors exhibited equivalent potency to their pinacol esters. Both benzoyl (Bz)-Phe-boroLeu and benzyloxycarbonyl (Cbz)-Leu-Leu-boroLeu pinacol ester inhibited 20 S and 26 S proteasomes with non-ideal behaviour, differences in inhibition of the two forms of proteasomes becoming apparent at high inhibitor concentrations (above 3×Ki). Both of these compounds were also potent inhibitors of 20 S and 26 S proteasomes in cultured cells. However, gel filtration of cell extracts prepared from cells treated with radiolabelled phenacetyl-Leu-Leu-boroLeu showed that only 20 S proteasomes were strongly labelled, demonstrating differences in the characteristics of inhibition of 20 S and 26 S proteasomes. The usefulness of peptidyl boronic acid inhibitors for investigations of proteasome-mediated protein degradation was confirmed by the observation that Bz-Phe-boroLeu and Cbz-Leu-Leu-boroLeu pinacol ester inhibited NFĸB activation with IC50 values comparable to their Ki values for purified proteasomes. The latter result supports the view that the chymotrypsin-like activity of proteasomes assayed with suc-Leu-Leu-Val-Tyr-AMC is a critical one for protein degradation in cells.

scholarly journals Cathepsin L plays a key role in SARS-CoV-2 infection in humans and humanized mice and is a promising target for new drug development

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Miao-Miao Zhao ◽  
Wei-Li Yang ◽  
Fang-Yuan Yang ◽  
Li Zhang ◽  
Wei-Jin Huang ◽  
...  
Keyword(s):  
Drug Development ◽  
Cathepsin L ◽  
Human Cells ◽  
New Drugs ◽  
Disease Course ◽  
Promising Target ◽  
First Time

AbstractTo discover new drugs to combat COVID-19, an understanding of the molecular basis of SARS-CoV-2 infection is urgently needed. Here, for the first time, we report the crucial role of cathepsin L (CTSL) in patients with COVID-19. The circulating level of CTSL was elevated after SARS-CoV-2 infection and was positively correlated with disease course and severity. Correspondingly, SARS-CoV-2 pseudovirus infection increased CTSL expression in human cells in vitro and human ACE2 transgenic mice in vivo, while CTSL overexpression, in turn, enhanced pseudovirus infection in human cells. CTSL functionally cleaved the SARS-CoV-2 spike protein and enhanced virus entry, as evidenced by CTSL overexpression and knockdown in vitro and application of CTSL inhibitor drugs in vivo. Furthermore, amantadine, a licensed anti-influenza drug, significantly inhibited CTSL activity after SARS-CoV-2 pseudovirus infection and prevented infection both in vitro and in vivo. Therefore, CTSL is a promising target for new anti-COVID-19 drug development.

scholarly journals Secreted KIAA1199 promotes the progression of rheumatoid arthritis by mediating hyaluronic acid degradation in an ANXA1-dependent manner

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Wei Zhang ◽  
Guoyu Yin ◽  
Heping Zhao ◽  
Hanzhi Ling ◽  
Zhen Xie ◽  
...  
Keyword(s):  
Rheumatoid Arthritis ◽  
Hyaluronic Acid ◽  
Dependent Manner ◽  
Collagen Induced Arthritis ◽  
Intracellular Degradation ◽  
Main Pathway ◽  
First Time

AbstractIn inflamed joints, enhanced hyaluronic acid (HA) degradation is closely related to the pathogenesis of rheumatoid arthritis (RA). KIAA1199 has been identified as a hyaladherin that mediates the intracellular degradation of HA, but its extracellular function remains unclear. In this study, we found that the serum and synovial levels of secreted KIAA1199 (sKIAA1199) and low-molecular-weight HA (LMW-HA, MW < 100 kDa) in RA patients were significantly increased, and the positive correlation between them was shown for the first time. Of note, treatment with anti-KIAA1199 mAb effectively alleviated the severity of arthritis and reduced serum LMW-HA levels and cytokine secretion in collagen-induced arthritis (CIA) mice. In vitro, sKIAA1199 was shown to mediate exogenous HA degradation by attaching to the cell membrane of RA fibroblast-like synoviosytes (RA FLS). Furthermore, the HA-degrading activity of sKIAA1199 depended largely on its adhesion to the membrane, which was achieved by its G8 domain binding to ANXA1. In vivo, kiaa1199-KO mice exhibited greater resistance to collagen-induced arthritis. Interestingly, this resistance could be partially reversed by intra-articular injection of vectors encoding full-length KIAA1199 instead of G8-deleted KIAA119 mutant, which further confirmed the indispensable role of G8 domain in KIAA1199 involvement in RA pathological processes. Mechanically, the activation of NF-κB by interleukin-6 (IL-6) through PI3K/Akt signaling is suggested to be the main pathway to induce KIAA1199 expression in RA FLS. In conclusion, our study supported the contribution of sKIAA1199 to RA pathogenesis, providing a new therapeutic target for RA by blocking sKIAA1199-mediated HA degradation.

Characterization of a factor that stimulates hydrolysis of GTP bound to ras gene product p21 (GTPase-activating protein) and correlation of its activity to cell density

1988 ◽  
Vol 8 (10) ◽  
pp. 4169-4173
Author(s):  
M Hoshino ◽  
M Kawakita ◽  
S Hattori
Keyword(s):  
Gene Product ◽  
Cell Density ◽  
Cultured Cells ◽  
Specific Activity ◽  
Gtpase Activating Protein ◽  
Ras Gene ◽  
Cell Extracts ◽  
Mouse Tissues ◽  
Almost All ◽  
Hydrolysis Of

The postmicrosomal fraction of the extract from NIH 3T3 and BALB/c 3T3 cells stimulated the hydrolysis of GTP bound to H-ras gene product p21 by severalfold. The stimulation was observed with normal p21 but not with p21 with valine as the 12th residue. This specificity is similar to that of GTPase-activating protein (GAP) for N-ras p21 described by M. Trahey and F. McCormick (Science 238:542-545, 1987). Consistent with this specificity, analysis of p21-bound nucleotides in living cells revealed that almost all normal p21 bound GDP, whereas oncogenic mutant p21s bound both GTP and GDP. Similar activity was also found in various mouse tissues, with brain tissue showing the highest specific activity. When cell extracts were prepared from cultured cells, there was a linear relationship between GAP activity and cell density. These results suggest the factor is involved in the regulation of cell proliferation.

scholarly journals Extensive non-canonical phosphorylation in human cells revealed using strong-anion exchange-mediated phosphoproteomics

2017 ◽  
Author(s):  
Gemma Hardman ◽  
Simon Perkins ◽  
Zheng Ruan ◽  
Natarajan Kannan ◽  
Philip Brownridge ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Protein Phosphorylation ◽  
Anion Exchange ◽  
Human Cell ◽  
Cell Biology ◽  
Human Cells ◽  
Phosphopeptide Enrichment ◽  
Cell Extracts ◽  
Strong Anion Exchange ◽  
Acid Labile

Protein phosphorylation is a ubiquitous post-translational modification (PTM) that regulates all aspects of life. To date, investigation of human cell signalling has focussed on canonical phosphorylation of serine (Ser), threonine (Thr) and tyrosine (Tyr) residues. However, mounting evidence suggests that phosphorylation of histidine also plays a central role in regulating cell biology. Phosphoproteomics workflows rely on acidic conditions for phosphopeptide enrichment, which are incompatible with the analysis of acid-labile phosphorylation such as histidine. Consequently, the extent of non-canonical phosphorylation is likely to be under-estimated. We report an Unbiased Phosphopeptide enrichment strategy based on Strong Anion Exchange (SAX) chromatography (UPAX), which permits enrichment of acid-labile phosphopeptides for characterisation by mass spectrometry. Using this approach, we identify extensive and positional phosphorylation patterns on histidine, arginine, lysine, aspartate and glutamate in human cell extracts, including 310 phosphohistidine and >1000 phospholysine sites of protein modification. Remarkably, the extent of phosphorylation on individual non-canonical residues vastly exceeds that of basal phosphotyrosine. Our study reveals the previously unappreciated diversity of protein phosphorylation in human cells, and opens up avenues for exploring roles of acid-labile phosphorylation in any proteome using mass spectrometry.

Effect of microenvironment and cell-line type on carbohydrate-binding proteins of macrophage-like cells

1988 ◽  
Vol 66 (11) ◽  
pp. 1169-1176 ◽  
Author(s):  
Hans-Joachim Gabius ◽  
Katalin Vehmeyer
Keyword(s):  
Binding Proteins ◽  
Cultured Cells ◽  
Sodium Dodecyl ◽  
Carbohydrate Binding ◽  
Intercellular Interaction ◽  
Cell Extracts ◽  
Carbohydrate Binding Proteins ◽  
Sugar Receptors

The pattern of sugar inhibition of rosette formation, a model for intercellular interaction between cultured cells and glutaraldehyde-fixed, trypsinated rabbit erythrocytes, served to infer the presence of carbohydrate-binding proteins. This profile from cell extracts for the two murine macrophage-like cell lines, P388D1 and J774A.1, was comparatively analyzed by affinity chromatography on supports with immobilized carbohydrates (lactose, L-fucose, N-acetyl-D-glucosamine, N-acetyl-D-galactosamine, and maltose) or with the immobilized mannose-rich yeast glycoprotein mannan or fetuin-derived glycopeptides containing sialic acid residues. After elution with specific sugar in the absence of Ca2+ ions, the proteins were separated by sodium dodecyl sulfate – polyacrylamide slab gel electrophoresis. The composition of carbohydrate-binding proteins of the two lines clearly exhibited quantitative and qualitative differences. Moreover, the pattern of P388D1 cells was also demonstrated to change significantly in response to alterations in the conditions of the physiological environment. These alterations were imposed by in vitro growth, by subsequent in vivo growth in nude mice, and by re-adaptation of cells to culture after in vivo passage. Collectively, our observations and other physiological and biochemical reports on macrophage lectins indicate that the presence of sugar receptors with different specificities may be an indicator of macrophage differentiation, being reversibly modulated to a considerable extent by external factors, e.g., microenvironment. Extensive but selective alterations in this respect could play an important role in the control of recognition and effector mechanisms within diverse functions of macrophage subpopulations.

scholarly journals Lysosomal degradation of glycoproteins and glycosaminoglycans. Efflux and recycling of sulphate and N-acetylhexosamines

1986 ◽  
Vol 235 (3) ◽  
pp. 707-713 ◽  
Author(s):  
L H Rome ◽  
D F Hill
Keyword(s):  
Cultured Cells ◽  
The Other ◽  
Biosynthetic Pathways ◽  
Significant Extent ◽  
Lysosomal Degradation ◽  
Intact Cells ◽  
Diploid Fibroblasts ◽  
Human Diploid Fibroblasts ◽  
Glycoprotein Degradation ◽  
Macromolecule Degradation

Lysosomal degradation of the carbohydrate portion of glycoproteins and glycosaminoglycans produces monosaccharides and sulphate, which must efflux from the lysosomes before re-entering biosynthetic pathways. We examined the degradation of glycoproteins and glycosaminoglycans by lysosomes isolated from cultured human diploid fibroblasts. Cells were grown for 24 h in medium containing [3H]glucosamine and [35S]sulphate. When lysosomes are isolated from these cells, they contain label primarily in macromolecules (glycoproteins and glycosaminoglycans). Glycoprotein degradation by isolated lysosomes was followed by measuring the release of tritiated sugars from macromolecules and efflux of these sugars from the organelles. Glycosaminoglycan degradation was monitored by the release of both tritiated sugars and [35S]sulphate. During macromolecule degradation, the total amounts of free [35S]sulphate, N-acetyl[3H]glucosamine and N-acetyl[3H]galactosamine found outside the lysosome parallels the amounts of these products released by degradation. The total degradation of glycoproteins and glycosaminoglycans by intact cultured cells was also examined. The lysosomal contribution to degradation was assessed by measuring inhibition by the lysosomotropic amine NH4Cl. After 48 h incubation, inhibition by NH4Cl exceeded 55% of glycoprotein and 72% of glycosaminoglycan degradation. Recycling of [3H]hexosamines and [35S]sulphate by intact cells was estimated by measuring the appearance of ‘newly synthesized’ radioactively labelled macromolecules in the medium. Sulphate does not appear to be appreciably recycled. N-Acetylglucosamine and N-acetylgalactosamine, on the other hand, are reutilized to a significant extent.

Plasminogen Activator (PA) Activity In Metastatic Cells: An Amidolytic Approach

1981 ◽  
Author(s):  
D Coen ◽  
A Bini ◽  
G Balconi ◽  
F Delaini ◽  
L Mussoni ◽  
...  
Keyword(s):  
Primary Tumor ◽  
Fibrinolytic Activity ◽  
Tumor Tissue ◽  
Cultured Cells ◽  
Cell Extracts ◽  
Mechanical Disruption ◽  
Metastatic Cells ◽  
Triton X ◽  
Selection Of

It has been proposed that fibrinolytic activity can play an important role in the process of metastasis formation. Nevertheless, it is not yet clear in which phase of the tumor growth and dissemination this activity is involved. We measured the fibrinolytic activity of cells from primary tumor and metastatic nodules of 3LL, an i.m. implanted murine tumor which selectively metastasizes to the lungs. Tumor cells have been studied both immediately after mechanical disruption of tumor tissue and after in vitro culturing to confluence. Their P.A. activity was tested by an amidolytic assay in which cells were incubated with purified plasminogen (3CU/ml) and 4mM S-2251 (Kabi Diagnostica, Stockholm, Sweden), a plasmin specific chromogenic substrate. After 3 hour incubation at 37°C, the reaction was stopped with acetic acid and absorbance read at 405 nm.Cells from the primary tumor and metastatic nodules showed a similar fibrinolytic activity, which was in both cases in- increased 3 to 4 fold in cell extracts obtained after preincubation with TRITON X-100. A dose-response curve plotted with increasing urokinase concentrations showed a parallel course. This data suggests that, in the 3LL model, PA activity is not one of the properties characterizing the selection of metastatic cells.On the other hand,cultured cells presented consistently higher levels of PA than their native counterparts, suggesting that adhesion of cells in culture may stimulate PA production or, alternatively, that cultured cells are a selected population in comparison to the overall number of native cells.

scholarly journals Hereditary spastic paraplegia SPG8 mutations impair CAV1-dependent, integrin-mediated cell adhesion

2020 ◽  
Vol 13 (613) ◽  
pp. eaau7500 ◽  
Author(s):  
Seongju Lee ◽  
Hyungsun Park ◽  
Peng-Peng Zhu ◽  
Soon-Young Jung ◽  
Craig Blackstone ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Hereditary Spastic Paraplegia ◽  
Cultured Cells ◽  
Protein Abundance ◽  
Missense Mutations ◽  
Spastic Paraplegia ◽  
Lysosomal Degradation ◽  
Actin Nucleation ◽  
Cellular Pathogenesis ◽  
Syndrome Protein

Mutations in WASHC5 (also known as KIAA0196) cause autosomal dominant hereditary spastic paraplegia (HSP) type SPG8. WASHC5, commonly called strumpellin, is a core component of the Wiskott-Aldrich syndrome protein and SCAR homolog (WASH) complex that activates actin nucleation at endosomes. Although various other cellular roles for strumpellin have also been described, none account for how SPG8-associated mutations lead to HSP. Here, we identified protein interactors of the WASH complex by immunoprecipitation and mass spectrometry and assessed the functions of strumpellin in cultured cells using both overexpression and RNA interference along with cell-spreading assays to investigate cell adhesion. We uncovered a decrease in CAV1 protein abundance as well as endosomal fission defects resulting from pathogenic SPG8 mutations. CAV1, a key component of caveolae, interacted with strumpellin in cells, and strumpellin inhibited the lysosomal degradation of CAV1. SPG8-associated missense mutations in strumpellin did not rescue endosomal tubulation defects, reduction in CAV1 protein abundance, or integrin-mediated cell adhesion in strumpellin-deficient cells. Mechanistically, we demonstrated that the WASH complex maintained CAV1 and integrin protein amounts by inhibiting their lysosomal degradation through its endosomal actin nucleation activity. In addition, the interaction of strumpellin with CAV1 stimulated integrin recycling, thereby promoting cell adhesion. These findings provide a molecular link between WASHC5 mutations and impairment of CAV1- and integrin-mediated cell adhesion, providing insights into the cellular pathogenesis of SPG8.

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